The present invention relates to an image forming unit and an image forming apparatus.
In a conventional image forming apparatus such as a printer, a copier, a facsimile, and the likes, a charge roller charges a surface of a photosensitive drum as a first image forming member, and an LED (Light Emitting Diode) head exposes the surface of the photosensitive drum to form a static latent image thereon. Then, a developing roller as a second image forming member attaches a thin layer of toner to the static latent image through static electricity, thereby forming a toner image. A transfer roller transfers the toner image to a sheet, thereby forming an image. After the transfer roller transfers the toner image to the sheet, a cleaning device removes toner remaining on the photosensitive drum (refer to Patent Reference).    Patent Reference: Japan Patent Publication No. 2002-108089
In the conventional printer, when it is difficult to accurately set a distance between an axis of the photosensitive drum and an axis of the developing roller due to a manufacturing variance, it is difficult to obtain a precise nip amount between the photosensitive drum and the developing roller, thereby deteriorating image quality.
Further, even though the distance between the axis of the photosensitive drum and the axis of the developing roller is controlled at a specific value in an initial stage of the conventional printer, an outer diameter of the photosensitive drum or the developing roller may decrease due to surface ware after the conventional printer is used for a long period of time. In this case, it is difficult to obtain a specific nip amount, thereby deteriorating image quality.
In view of the problem described above, an object of the invention is to provide an image forming unit and an image forming apparatus, in which it is possible to solve the problems of the conventional printer. In the image forming unit and the image forming apparatus of the present invention, it is possible to accurately obtain a specific nip amount between a first image forming member and a second image forming member.
Further objects of the invention will be apparent from the following description of the invention.